遇到这个问题，在网上找了各种方法，经过实际操作，下述方式能够解决此问题。
1.修改 web.xml
修改为：
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">
</web-app>
2.Window>Show View>Navigator,在Navigator下打开项目的.settings目录下org.eclipse.jdt.core.prefs,修改为：
eclipse.preferences.version=1
org.eclipse.jdt.core.compiler.codegen.inlineJsrBytecode=enabled
org.eclipse.jdt.core.compiler.codegen.targetPlatform=1.8
org.eclipse.jdt.core.compiler.compliance=1.8
org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
org.eclipse.jdt.core.compiler.problem.forbiddenReference=warning
org.eclipse.jdt.core.compiler.source=1.8
3.打开org.eclipse.wst.common.component，修改为：
<?xml version="1.0" encoding="UTF-8"?><project-modules id="moduleCoreId" project-version="1.8.0">
<wb-module deploy-name="storm">
<wb-resource deploy-path="/" source-path="/target/m2e-wtp/web-resources"/>
<wb-resource deploy-path="/" source-path="/src/main/webapp" tag="defaultRootSource"/>
<wb-resource deploy-path="/WEB-INF/classes" source-path="/src/main/java"/>
<wb-resource deploy-path="/WEB-INF/classes" source-path="/src/main/resources"/>
<wb-resource deploy-path="/WEB-INF/classes" source-path="/src/test/java"/>
<wb-resource deploy-path="/WEB-INF/classes" source-path="/src/test/resources"/>
<property name="context-root" value="storm"/>
<property name="java-output-path" value="/storm/target/classes"/>
</wb-module>
</project-modules>
4.打开org.eclipse.wst.common.project.facet.core.xml，修改为：
<?xml version="1.0" encoding="UTF-8"?>
<faceted-project>
<fixed facet="wst.jsdt.web"/>
<installed facet="jst.web" version="3.0"/>
<installed facet="wst.jsdt.web" version="1.0"/>
<installed facet="java" version="1.8"/>
</faceted-project>
保存后，打开project facets，则问题消失。